ABSTRACT The effect of solution annealing and aging treatment on the intergranular carbide precipitation behavior of alloy 690 tubes for steam generators is investigated. The carbides precipitated on the grain boundaries were identified as chromium-rich M23C6 carbide, which has a cube-cube orientation relationship with the matrix on one side of neighboring grains. The carbide precipitation behavior is closely related to the interaction between the solubility of carbon in Ni-based matrix and diffusion of alloying elements. The ultimate tensile strength and elongation of the solution annealed alloy 690 tubes at 300°C are 638.8 ± 12.4 MPa and 43.2 ± 4.2%, respectively. In the early stage of precipitation, the ultimate tensile strength increased to 720.4 ± 13.5 MPa. The carbides function as reinforcement in alloy 690 and provide strength enhancement with aging time reached 15 hours. However, when the aging time passed 15 hours, this property gradually decreased to 710.6 ± 12.6 MPa due to the low bonding strength between the carbide and matrix.

中文翻译：

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M23C6碳化物析出行为及其对Ni基690合金力学性能的影响

摘要 研究了固溶退火和时效处理对蒸汽发生器用 690 合金管晶间碳化物析出行为的影响。析出在晶界上的碳化物被鉴定为富铬M23C6碳化物，与相邻晶粒一侧的基体呈立方体取向关系。碳化物析出行为与碳在镍基基体中的溶解度和合金元素扩散之间的相互作用密切相关。固溶退火 690 合金管在 300°C 下的极限拉伸强度和伸长率分别为 638.8±12.4 MPa 和 43.2±4.2%。在沉淀初期，极限抗拉强度增加到720.4±13.5 MPa。碳化物在合金 690 中起到增强作用，并在时效时间达到 15 小时时提供强度增强。然而，当时效时间超过 15 小时时，由于碳化物与基体之间的结合强度较低，该性能逐渐下降至 710.6±12.6 MPa。